In many fields of human medicine or medical research, secure fixing/immobilization/splinting or compression and/or molding of the patient or parts of the patient or the (mechanical) attachment of devices or appliances is necessary. This is of particularly great significance not only in the field of diagnostic and therapeutic radiology, radiation therapy, or in the case of operative/surgical interventions (neurosurgery, ENT, orthopedics, etc.), but also in the preoperative or postoperative care of wounds/injuries.
Through the incorporation of computer technology in diagnosis and therapy, the requirements have risen for the precision and reproducibility both during the fixing of a stereotactic frame system onto a patient and also during the immobilization of the body itself. Comfort, rapid application, mobility, and cost are significant advantages of the present invention.
The following types of immobilization are known as the prior art:
a) Immobilization of the body using bands or cuffs: In this case, the body of the patient lies on a foam underlay and bands are stretched transversely over the body to immobilize the patient onto the underlay. However, the following points are some of the disadvantages of this approach:
Pressure points, shifting, and/or skin swelling can occur due to strong tension of the bands (non-homogeneous pressure distribution);
After removal of the retaining elements (bands), repeated immobilization in precisely the same location is virtually impossible, which is disadvantageous in particular in the case of stereotactic operations and in radiation therapy;
The body is not sufficiently fixed; particularly in the lateral direction; position cannot be restricted or defined sufficiently.
b) Immobilization of the body by screw connections to the bones: The body of the patient is screwed at multiple points to a metal frame. The following points are disadvantageous in this case:
The screw connection to the bone represents an invasive method and is therefore only possible and justified in the case of specific indications;
The mental stress of the patient is substantial;
The method is only applicable to specific mountings of the patient and obstructs medical operations;
Immobilization of the soft tissue parts (muscles, ligaments, connective tissue) is practically impossible.
c) Immobilization by formwork: In this case, the patient is laid on a type of “air mattress”, which is filled with foam beads. Upon suctioning out the air from this mattress, it solidifies by pressing the foam beads against one another. The vacuum mattress is initially adapted in the first step and then suctioned out further in the second step. An imprint of the body is obtained by this method. In this method, it is disadvantageous that:
The typically used “mattresses” restrict patient motion, but do not result in actual immobilization;
The body is solely held in position by gravity or by compression bands, so that no fixed connection exists between the surfaces;
In the case of uncooperative patients, sufficient immobilization is practically impossible;
Precise molding is also not possible, since in practice the mattress cannot be applied precisely to all body parts;
Pressure points often arise due to wrinkling or excessively strong contact pressure, which can result in tissue injuries particularly in sedated patients.
d) Vacuum fixation system: In vacuum fixation systems, the molding element is applied to the body via vacuum. By suctioning out the air between the molding element and patient surface, a good connection for molding and fixation can be provided. In this case, it is disadvantageous that:
A vacuum pump must run continuously, so that the connection between molding element and patient is maintained;
The system is complex, not easy to handle, and difficult to transport;
In the case of interventions which require a high level of asepsis or even sterility, the air stream of the vacuum pump represents a hazard (bacteria entrainment);
Higher connecting forces and therefore improved molding and immobilization are not possible, because injuries (e.g., reduced blood perfusion, effusion of blood) may arise due to excessively high and long-lasting pressures;
In the event of failure of the vacuum, the connection is lost. This is critical in particular if, for example, a hazard to life and limb of the patient can arise or the (surgical/radiological) intervention must be terminated or interrupted in the event of loss of the connection;
The method is complex overall and is hardly practicable in particular for radiological/surgical interventions.
Other techniques such as splints, thermoplastic material, plastic imprint, plaster casts, etc., have similar disadvantages. In addition, these methods also entail substantial financial or chronological outlay and are therefore only used for long-term applications.